Metabolism of Vitamin B12 and Causes of B12 Deficiency

Overview of Vitamin B12

Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for various biochemical processes in the human body. It plays a vital role in DNA synthesis, red blood cell production, and neurological function.

Structure and Sources of Vitamin B12

Vitamin B12 consists of a corrin ring with a cobalt atom at its center, making it unique among vitamins. It is primarily obtained from animal products such as meat, dairy, and eggs. Certain bacteria synthesize B12, making it bioavailable through dietary sources.

Metabolism and Absorption of Vitamin B12

Vitamin B12 absorption involves several steps:

• Gastric acid and pepsin release B12 from food.
• Intrinsic factor (IF) binds to B12 in the small intestine.
• Absorption occurs in the ileum via receptor-mediated endocytosis.
• Stored primarily in the liver, B12 has a long biological half-life.

Causes of Vitamin B12 Deficiency

B12 deficiency can arise due to multiple factors:

Dietary Deficiency

Vegans and individuals with poor dietary intake may lack adequate B12.

Malabsorption Syndromes

Conditions such as pernicious anemia, Crohn's disease, and celiac disease hinder absorption.

Medications

Long-term use of proton pump inhibitors (PPIs) and metformin can contribute to deficiency.

Genetic Disorders

Genetic mutations affecting B12 transport can lead to functional deficiency.

Clinical Manifestations of B12 Deficiency

Common symptoms include:

• Neurological issues: Tingling sensations, memory impairment, depression.
• Hematological effects: Megaloblastic anemia, fatigue, pallor.
• Gastrointestinal symptoms: Glossitis, loss of appetite.

Diagnosis and Treatment

Diagnostic tests include serum B12 levels, methylmalonic acid, and homocysteine tests. Treatment involves dietary supplementation and intramuscular B12 injections for severe cases.

Conclusion

Vitamin B12 is crucial for maintaining health, and its deficiency can lead to serious complications. Awareness, proper diagnosis, and timely intervention are key to preventing deficiency-related disorders.